Apparatus for processing cathode ray tubes



Dec. 31, 1963 J. F. STEWART 3,115,732

APPARATUS FOR PROCESSING CATHODE RAY TUBES Filed Sept. 26, 1961 United States Patent 3,115,732 APPARATUS FOR PROCESSING CATHODE RAY TUBES John F. Stewart, Marion, Ind, assignor to Radio Corporation of America, a corporation of Delaware Filed Sept. 26, 1961, Ser. No. 140,813 6 Claims. (Cl. 5388) This invention relates to apparatus for processing electron tubes and particularly to cart apparatus for transporting cathode ray tube bulbs through bake-out and exhaust processing steps in the fabrication thereof.

In fabricating cathode ray tubes, a phosphor screen and various conductive coatings are applied to the internal Walls of the bulb, and an electron gun is sealed into the bulb. The cathode ray tube, open to the atmosphere through a small exhaust tubulation, is then usually mounted on a cart and the exhaust tubulation is connected to an exhaust system, which includes a pump carried by the cart. The cart is passed through an elongated oven on tracks. Electrical terminals on the cart make continuous contact with bus bars along the tracks so as to energize the exhaust pump thereon. The cathode ray tube bulb is passed through the oven to bake and out-gas the internal surfaces of the bulb and electron gun therein during which time it is being exhausted through the exhaust tubulation. After a suitable evacuation has been obtained, the exhaust tubulation is pinched or closed off by means carried on the cart. Exhaust cart apparatus of this general type is well known in the art.

In order to secure a good, temporary vacuum-tight seal between the exhaust tubulation and exhaust system on the cart, the tubulation is fitted snugly into a cylindrical opening (exhaust port) of a compression head which is connected to the exhaust pump. To prevent breakage of the tubulation or adjacent portions of the bulb, the tubulation and the exhaust port must be maintained aligned throughout the transport of the bulb on the cart.

In order to avoid misalignment of the bulb tubulation and the exhaust port, in the prior art, the attempt has been made to align the bulb support means on the cart with the compression head into which the tubulation is received, and then rigidly to fix these members relative to each other. However, the results of such attempts have not been satisfactory; excessive breakage often occurred because of a misaligned bulb and compression head. Such misalignment is believed to result from a gradual loss of alignment between the bulb support and compression head through extended use, or even when the bulb support and the compression head are aligned, from imperfectly formed bulbs or bulb vibration during transport on the cart.

Accordingly, it is an object of this invention to provide improved cart apparatus for transporting cathode ray tube bulbs through bake-out and exhaust processing steps, which apparatus reduces bulb breakage as encountered in the use of prior art apparatus.

According to my invention, the compression head of an exhaust cart is resiliently mounted on the frame of the cart while the bulb support is mounted on the frame so as to be laterally rigid relative to the intended axis of alignment of the exhaust tubulation with the compression head. The compression head may, for example, be mounted on the cart frame with rubber bushings, springs, or other known resilient means.

It is true that by virtue of a resilient mounting, the compression head can be moved off the intended alignment axis When a bulb tubulation is not disposed therein and thus destroy the desired alignment. On the other hand, when a bulb tubulation is disposed in the compression head, whether the tubulation is on axis or off axis due to an imperfectly formed bulb, a vibrated bulb, or an offaxis bulb support, the resiliently mounted compression head can adjust to the condition to provide alignment of itself with the tubulation. Experience has shown that the force necessary to move the compression head to maintain alignment with the tubulation is less than that necessary to break the tubulation. Thus the tubulation can move the compression head to carry the head along with the tubulation and thus maintain the necessary alignment even when the tubulation is oif-axis.

In the drawings:

FIG. 1 is a side elevation of an exhaust cart apparatus made according to the invention with a cathode ray tube thereon; and

IG. 2 is an enlarged elevation partially in section of a portionof the apparatus of FIG. 1.

Referring to the drawings, an exhaust cart '10 is adapted to be moved along a pair of rails 12 on wheels 13 and carry a cathode ray tube bulb 14 of conventional design through an elongated oven (not shown) for baking out and exhausting the bulb 14.

The cart 10 comprises a frame 16 having a lower platform 18 and a middle platform 20. Extending upwardly from the middle platform 20 are a pair of rigid hollow posts 22, the upper ends of which are rigidly tied together by an upper platform 24. Bushings 26 are attached to both the upper and lower ends of the posts 22. A pair of support rods 28 are slidably mounted in the bushings 26 and posts 22. The support rods 28 extend downwardly beneath the middle platform 20 and engage a pair of springs 30 which are fixed to the middle platform 20. A bulb cradle 32 is attached to the upper ends of the support rods 28 for receiving the cathode ray tube bulb 14' therein in a neck down position. When a bulb 14 is placed in the cradle 3-2, the support rods 28- slide downwardly against the supporting force of the springs 30. A rigid bar 34 connects the upper ends of the support rods 28 together to prevent their spreading apart when a bulb 14 is disposed in the cradle 32.

Mounted on the lower platform 18 is a roughing or backer exhaust pump 36 which is driven by an electric motor 38 coupled thereto by a belt 40. The suction port of the backer pump 36 is connected through a pipe 42 to an exhaust port of a diffusion pump 44-. The suction port end of the diffusion pump 44 is in turn directly attached to a compression head 46.

- The upper end of the compression head 46 is provided with an exhaust port assembly 48 into which a tubulation 49 of the cathode ray tube bulb E14 is received in a temporary vacuum-tight relationship. The exhaust port assembly 48, which is conventional and known in the industry, may comprise a thick, massive, rubber washer having a central opening into which the tubulation 49 is coaxially received and which is longitudinally compressible by a screw-type fitting to radially compress the rubber Washer against the tubulation 49.

The compression head 46 extends through an opening 54) in the middle platform 20 and is mounted thereon in a manner best shown in FIGURE 2. A radially extending flange 51 ;of the compression head 46 rests upon resilient means 52, such as \a pair of springs or rubber blocks. The compression head 46 is loosely secured to the middle platform 20 by a pair of bolts 54 extending through the flange 5 1, the resilient means 52, and the middle platform 20. Nuts 56 are screwed onto the bolts 54 but preferably are not tightened against the middle platform 21 The compression head 46 and diffusion pump '44 are :thus loosely, resiliently mounted on the middle platform 20 in such a Way that they are free to be tiltably moved with respect thereto. The compression head is therefore resiliently mounted with respect to the rigidly mounted cathode .ray tube bulb 14 and the exhaust tubulati'on 49 thereof.

An RF heater coil 57 is mounted on the upper platform 24 in a position to encircle the neck of the bulb 14 in a selected region of an electron gun (not shown) contained therein. The coil 57 is energizable to generate heat in certain of the gun parts to drive out undesirable gases occluded therein.

An electric radiant heater 58 is supported from the upper platform 24 and is disposed so as to encircle the tu'bulation 49 adjacent the neck of the bulb. The radiant heater 58 is operable to soften the glass tubulation 49 to ermit a tip-off or closing and severing thereof. In the tip-off operation, after the tubulation is thus softened an operator inserts a forked lever under the bulb and gently raises it to cause a closing and severing of the softened glass tubulation.

Mounted on the lower platform 18 of the cart is a water pump and electrical motor unit 59. The suction inlet of the pump 59 is connected to a pipe 60 which extends downwardly beneath the lower platform 18 of the cart and into a Water filled trough 62 which extends between and along the tracks 12. Water which is pumped from the trough 62 is fed through a discharge pipe 64 from the pump 59 to the exhaust port assembly 48 of the compression head 56 and irom thence, through pipe 66 to the RF 'coil 57. From the RF coil 57, the water is passed through a pipe 76 which is wound in heat transfer relationship about the diffusion pump 44. From thence, the pipe 70 extends to beneath the lower platform 18 Where the circulated Water is returned to the trough 62. The circulating water serves to cool the exhaust port assembly 48, the RF coil 57, and the diffusion pump 44.

An air blower and electrical motor unit 72 is mounted on a horizontal member 73 of the frame 16 and so disposed to air cool the lower portion of the diffusion pump 44 during the time the cart is being returned to the load position.

Electrical power for the backer pump motor 38, the water pump 58, the blower '72, and the radiant heater 58 is supplied through a plural-contact terminal 74 which contacts a plurality of bus bars. extending along the tracks 12. The contacts of the terminal 7 4 are connected to a control and distribution box 76 to which the various electrical devices are connected (by connections not shown). The RF coil 57 is connected to a plurality of contact bars 78 on the cart 10 which engage spring contacts (not shown) mounted on the oven frame.

As hereinbefore stated, prior art attempts to maintain alignment between the bulb tubulation and the compression head, involved aligning the bulb support with the compression head and then rigidly fixing these members relative to each other. Accurate rigid alignment was thought necessary to avoid bulb breakage. It was reasonable to assume that a resilient mounting of the compression head might permit it to be moved out .of alignment with the tubulation and thus strain and possibly break the tubulation. Therefore, it was concluded that a resilient mounting of either the compression head or the bulb was not the thing to do, but rather that alignment should be maintained by a rigid mounting (of the bulb support and the compressionhead.

The concept of a resiliently mounted compression head for solving the problems described above is contrary to these prior teachings of those skilled in the art as exemplified by the prior art solutions. Moreover, when incorporated in the manufacture of cathode ray tubes, the present invention provided in one instance an unexpected reduction of breakage of about 75% for 27 inch bulbs and a reduction by varying amounts in the order of 50% for smaller bulbs.

I claim:

1. Apparatus for exhausting an electron tube bulb comprising a bulb support for supporting said bulb against movement lateral :to a predetermined axis and. exhaust means including a diffusion pump and a compression head having an exhaust port assembly connectable to said bulb supported by said bulb support, said diffusion pump and compression head being rigidly attached to each other and resiliently mounted to move laterally with respect to said axis to be self-aligning with said bulb.

2. Apparatus for exhausting an electron tube bulb through an exhaust tubul-ation thereof, said apparatus comprising a frame, a bulb support fixedly mounted on said frame against movement relative thereto laterally to a fixed alignment axis, said bulb support being adapted to support said electron tube with its tubulation disposed on said axis, a compression head resiliently mounted for lateral movement on said frame and having an exhaust port disposed substantially on and in alignment with said axis for receiving said tubulation when said bulb is supported by said bulb support, and exhaust pump means connected to said compression head for evacuating a bulb having its :tubulation received in said port.

3. Apparatus for transporting through bake.out and exhaust processing steps a cathode ray tube bulb having a cylindrical exhaust tubulation, said apparatus comprising a cart including a frame, first means mounted on said frame for supporting said bulb with said tubulation aligned with a fixed alignment axis, said first means being movable re ative to said frame only in a direction parallel with said axis, second means resiliently mounted on said frame and having a cylindrical port for receiving said ltu-bulation, the resilient mounting of said second means being such as to permit said port to move into and out of alignment with said axis, and third means connected to said second means for evacuating said bulb through said tubulation and said second means.

4. Apparatus for transporting a cathode ray tube bulb through bake-out and exhaust processing steps, said bulb having an exhaust tubulation extending therefrom, said apparatus comprising a frame, means enabling said frame to be moved along a prescribed path, a bulb support mounted on said frame and including a cradle for receiving said bulb with said tubulation aligned with a predetermined axis and a pair of parallel legs longitudinally slidable relative to said frame parallel to said axis and fixed against movement relative to said frame lateral to said axis, a compression head resiliently mounted on said frame, said compression head including an exhaust port assembly having an exhaust port therein for receiving said tubulation, said exhaust port being aligned on said axis and movable laterally and longitudinally with respect to said axis within limits as provided by the resilient mounting of said compression head on said frame, and exhaust pump means connected to said compression head, whereby a cathode ray tube bulb supported by said bulb support with its tubulation received in said exhaust port can be evacuated.

5. Apparatus for exhausting an electron tube bulb having an exhaust tubulation attached thereto, said apparatus comprising a frame, a platform mounted on said frame, a bulb supporting member resiliently and slidably mounted on said frame and adapted to support a bulb with the exhaust tubulation on a predetermined axis, said supporting member having movement parallel only to said axis, an exhaust assembly having a port registering with said axis and adapted to receive said exhaust tubulation, said exhaust assembly being resiliently mounted on said platform and capable of movement laterally of said axis.

6. Apparatus for exhausting an electron tube having an exhaust tubulation attached thereto, said apparatus comprising a frame, a pair of vertically positioned hollow tubular members mounted on said frame, a bulb supporting assembly having members slidably mounted within said hollow tubular members and resiliently supported therein and adapted to support said bulb and tubulation on a predetermined vertical axis, said bulb supporting by said bulb support, said exhaust assembly being capable of movement laterally of said axis.

References Cited in the file of this patent UNITED STATES PATENTS McGowan Oct. 11, 1938 Carter Jan. 16, 1951 

1. APPARATUS FOR EXHAUSTING AN ELECTRON TUBE BULB COMPRISING A BULB SUPPORT FOR SUPPORTING SAID BULB AGAINST MOVEMENT LATERAL TO A PREDETERMINED AXIS AND EXHAUST MEANS INCLUDING A DIFFUSION PUMP AND A COMPRESSION HEAD HAVING AN EXHAUST PORT ASSEMBLY CONNECTABLE TO SAID BULB SUPPORTED BY SAID BULB SUPPORT, SAID DIFFUSION PUMP AND COMPRESSION HEAD BEING RIGIDLY ATTACHED TO EACH OTHER AND RESILIENTLY MOUNTED TO MOVE LATERALLY WITH RESPECT TO SAID AXIS TO BE SELF-ALIGNING WITH SAID BULB. 